The present invention relates to exhaust gas recirculation (EGR) systems, and more particularly, to an EGR system flexible gas connection pipe joint.
EGR systems are designed to recirculate exhaust gas generated by an internal combustion engine back into an engine intake stream. Since the exhaust gas exiting the engine is already combusted, it does not combust or burn again when it is recirculated back into the combustion chamber, thereby acting to displace some of the normal intake charge. The effect of adding such exhaust gas to the intake charge operates to chemically slow and cool the combustion process by several hundred degrees, thereby acting to reduce NOx formation.
For this reason, EGR systems have gained widespread acceptance and application for use with the many different types of gasoline and diesel internal combustion engines that are used to power vehicles such as cars and trucks. The addition of such an EGR system to heavy duty diesel engines requires that an additional exhaust connection port be configured that is positioned upstream of the turbocharger, i.e., before the entry point of exhaust gas from the engine into the turbine housing. The new connection port can either be configured as part of the turbocharger or as part of the exhaust manifold.
In such an EGR system application, the new connection port is coupled to an EGR valve (or other EGR system device) via suitable metal piping. A problem that arises with this connection configuration, however, is the fact that the two ends of the EGR system exhaust connection, i.e., between the hot pipe end from the connection point on the turbocharger or the exhaust manifold itself and the pipe connected to the EGR valve, are made from different types of metallic materials and/or are exposed to different operating temperatures, thereby having different thermal expansion and contraction characteristics during engine operation. Such differences in thermal expansion and contraction characteristics are know to cause three-dimensional movement between the two connection points, making the task of providing a leak-tight seal between the two very challenging.
Because the pipe does not run parallel to the engine, it does not expand in two dimensions, but rather expands and moves in a three-dimensional vector space. This makes the connecting joint challenging because one cannot use traditional slip joints as are used on exhaust manifolds.
It is, therefore, desirable that a new joint connection be configured that is capable of accommodating three-dimensional movement between the connecting ends of an EGR system known to occur during engine operating cycles. It is further desired that such new joint connection be relatively easy to install, without the need for special installation tools and the like.
The present invention is directed to a flexible joint for use in transporting exhaust gas in an EGR system. The flexible EGR joint or coupling is designed to accommodate the three-dimensional movement of connecting members caused from thermal effects of engine operation. A flexible connection joint, for use in an internal combustion engine exhaust gas transport system, comprises a hot pipe or connection with an exhaust gas source. The hot pipe has a first end for connecting with the exhaust gas source, and a second oppositely positioned end for connecting with an exhaust gas receiving member. The hot pipe second end has a generally cylindrical outside surface.
The flexible EGR joint includes an adapter that is coupled to the hot pipe second end for receiving exhaust gas therefrom. The adapter comprises a cylindrical inside diameter, and the hot pipe second end is disposed within the cylindrical inside diameter.
A key feature of this invention is the fact that the hot pipe second end has a radiused, i.e., barrel-shaped, outside surface. This radiused surface configuration is provided to enable lateral, i.e., three-dimensional, movement of the hot pipe second end within the adapter, thereby operating to accommodate the actual thermally-affected movement of the connection members.
A sealing means is interposed between the hot pipe end and the adapter to ensure a leak-tight seal therebetween during such movement. The sealing means can be in the form of a sealing ring that resides within a ring groove disposed within the hot pipe end outside surface. Alternatively, the sealing means can be in the form of one or more sealing rings or washers that are disposed around the hot pipe end outside surface. In either case, the sealing means operates to provide a leak-tight seal, thereby preventing the leakage of gas between opposed concentric hot pipe and adapter surfaces.